Teresa F. Fernandes

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects

The recent advances in nanotechnology and the corresponding increase in the use of nanomaterials in products in every sector of society have resulted in uncertainties regarding environmental impacts. The objectives of this review are to introduce the key aspects pertaining to nanomaterials in the environment and to discuss what is known concerning their fate, behavior, disposition, and toxicity, with a particular focus on those that make up manufactured nanomaterials. This review critiques existing nanomaterial research in freshwater, marine, and soil environments. It illustrates the paucity of existing research and demonstrates the need for additional research. Environmental scientists are encouraged to base this research on existing studies on colloidal behavior and toxicology. The need for standard reference and testing materials as well as methodology for suspension preparation and testing is also discussed.

Nanomaterials for environmental studies: Classification, reference material issues, and strategies for physico-chemical characterisation

NanoImpactNet is a European Commission Framework Programme 7 (FP7) funded project that provides a forum for the discussion of current opinions on nanomaterials in relation to human and environmental issues. In September 2008, in Zurich, a NanoImpactNet environmental workshop focused on three key questions: 1. What properties should be characterised for nanomaterials used in environmental and ecotoxicology studies? 2. What reference materials should be developed for use in environmental and ecotoxicological studies? 3. Is it possible to group different nanomaterials into categories for consideration in environmental studies? Such questions have been, at least partially, addressed by other projects/workshops especially in relation to human health effects. Such projects provide a useful basis on which this workshop was based, but in this particular case these questions were reformulated in order to focus specifically on environmental studies. The workshop participants, through a series of discussion and reflection sessions, generated the conclusions listed below. The physicochemical characterisation information identified as important for environmental studies included measures of aggregation/agglomeration/dispersability, size, dissolution (solubility), surface area, surface charge, surface chemistry/composition, with the assumption that chemical composition would already be known. There is a need to have test materials for ecotoxicology, and several substances are potentially useful, including TiO(2) nanoparticles, polystyrene beads labelled with fluorescent dyes, and silver nanoparticles. Some of these test materials could then be developed into certified reference materials over time. No clear consensus was reached regarding the classification of nanomaterials into categories to aid environmental studies, except that a chemistry-based classification system was a reasonable starting point, with some modifications. It was suggested, that additional work may be required to derive criteria that can be used to generate such categories, that would also include aspects of the material structure and physical behaviour.

Effects of Aqueous Exposure to Silver Nanoparticles of Different Sizes in Rainbow Trout

Despite increasing application of silver nanoparticles (NPs) in industry and consumer products, there is still little known about their potential toxicity, particularly to organisms in aquatic environments. To investigate the fate and effects of silver NPs in fish, rainbow trout (Oncorhynchus mykiss) were exposed via the water to commercial silver particles of three nominal sizes: 10 nm (N(10)), 35 nm (N(35)), and 600-1600 nm (N(Bulk)), and to silver nitrate for 10 days. Uptake into the gills, liver, and kidneys was quantified by inductively coupled plasma-optical emission spectrometry, and levels of lipid peroxidation in gills, liver, and blood were determined by measurements of thiobarbituric acid reactive substances. Expression of a suite of genes, namely cyp1a2, cyp3a45, hsp70a, gpx, and g6pd, known to be involved in a range of toxicological response to xenobiotics was analyzed in the gills and liver using real-time PCR. Uptake of silver particles from the water into the tissues of exposed fish was low but nevertheless occurred for current estimated environmental exposures. Of the silver particles tested, N(10) were found to be the most highly concentrated within gill tissues and N(10) and N(Bulk) were the most highly concentrated in liver. There were no effects on lipid peroxidation in any of the tissues analyzed for any of the silver particles tested, and this is likely due to the low uptake rates. However, exposure to N(10) particles was found to induce expression of cyp1a2 in the gills, suggesting a possible increase in oxidative metabolism in this tissue.

Management of environmental impacts of marine aquaculture in Europe

Abstract There are large differences between countries in the rate of growth and development of marine aquaculture, and also in the sophistication and complexity of its regulation, control and monitoring procedures. The potentially deleterious impacts of aquaculture are widely documented in the literature [J. Appl. Ichthyol. 17 (2001) 181; Fernandes, T.F., Eleftheriou, A., Ackefors, H., Eleftheriou, M., Ervik, A., Sanchez-Mata, A., Scanlon, T., White, P., Cochrane, S., Pearson, T.H., Miller, K.L., Read, P.A., 2002. The Management of the Environmental Impacts of Aquaculture. Scottish Executive, Aberdeen, UK, 88 pp.]. It is widely accepted that such impacts would be minimised or negated by the adoption of appropriate culturing procedures and environmental safeguards including regulatory, control and monitoring procedures [Nature Conservancy Council (NCC), 1989. Fish Farming and the Safeguard of the Natural Marine Environment of Scotland. Nature Conservancy Council, Peterborough, England, 136 pp.; Codling, I.D., Doughty, R., Henderson, A., Naismith, I., 1995. Strategies for Monitoring Sediments and Fauna Around Cage Fish Farms. Marlow, UK: Scotland and Northern Ireland Forum for Environmental Research (SNIFFER), Report No. SR 4018, 78 pp.; GESAMP (IMO/FAO/UNESCO-IOC/WMO/WHO/IAEA/UN/UNEP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection), 1996. Monitoring the ecological effects of coastal aquaculture wastes. Scientific aspects of marine environmental protection. Rome, Italy: Rep. Stud. GESAMP No. 57, 38 pp.; GESAMP (IMO/FAO/UNESCO-IOC/WMO/WHO/IAEA/UN/UNEP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection), 2001. Planning and management for sustainable coastal aquaculture development. Rome, Italy: Rep. Stud. GESAMP No. 68, 90 pp.]. It is essential that such safeguards are formulated from the best available science and technology and from the best available experience and expertise. In this context, there are lessons to be learned from the strategy and regulatory framework for the regulation, control and monitoring of environmental impacts of marine aquaculture within the European Union (EU). This paper identifies some of the main issues relevant to the management of environmental impacts of marine aquaculture; reviews EU and international policy and regulations in this context and provides one example of a strategy for the management of the environmental impacts of marine aquaculture by reference to the marine aquaculture industry in Scotland. In conclusion, it examines a number of current, key environmental concerns pertaining to the impact and regulation of marine aquaculture, which whilst being the subject of divergent views, are pivotal to the development of the industry. Recommendations for systems, procedures and research to address these concerns are identified. The paper is primarily concerned with marine finfish culture, although brief reference is made to shellfish culture. The control of diseases of finfish and shellfish is outside the scope of the paper, although brief consideration is given to current concerns relating to sea lice (predominantly Lepeophtheirus salmonis) infestations in salmonids.

The importance of life cycle concepts for the development of safe nanoproducts

Whilst the global players in industry are rapidly moving forward to take advantage of the new opportunities and prospects offered by nanotechnologies, it is imperative that such developments take place in a safe and sustainable manner. The increasing use of engineered nanomaterials (ENMs) in consumer products has raised certain concerns over their safety to human health and the environment. There are currently a number of major uncertainties and knowledge gaps in regard to behavior, chemical and biological interactions and toxicological properties of ENMs. As dealing with these uncertainties will require the generation of new basic knowledge, it is unlikely that they will be resolved in the immediate future. One has to consider the whole life cycle of nanoproducts to ensure that possible impacts can be systematically discovered. For example, life cycle assessment (LCA) - a formalized life cycle concept - may be used to assess the relative environmental sustainability performance of nanoproducts in comparison with their conventional equivalents. Other less formalized life cycle concepts in the framework of prospective technology assessment may uncover further detailed and prospective knowledge for human and environmental exposure to ENMs during the life cycle of nanoproducts. They systematically reveal impacts such as cross product contamination or dissipation of scarce materials among others. The combination of different life cycle concepts with the evolving knowledge from toxicology and risk assessment can mitigate uncertainties and can provide an early basis for informed decision making by the industry and regulators.

A comparison of nanoparticle and fine particle uptake by Daphnia magna

The use of nanoparticles in various applications is steadily on the rise, with use in a range of applications, including printer toner, sunscreen, medical imaging, and enhanced drug delivery. While research on human effects via, for example, inhalation is relatively well developed, the environmental assessment of nanoparticles is in its infancy. In the present study, we assessed the uptake and quantitative accumulation, as well as the depuration, of a model nanoparticle, a 20-nm fluorescent carboxylated polystyrene bead, in the aquatic invertebrate Daphnia magna and compared it to a larger, 1,000-nm particle. Using confocal microscopy, rapid accumulation in the gastrointestinal tract was observed within an hour of exposure to both particle sizes in both adults and neonates. Fluorescence could also be observed in the oil storage droplets, suggesting that both particle sizes have crossed the guts epithelial barrier. Quantification of fluorescence of both sizes of particles showed that although uptake of the 20-nm particles was lower in terms of mass it was equal to or greater than 1000-nm particle uptake when expressed as surface area or particle number. Depuration was relatively rapid for the 1000-nm beads, decreasing by more than 90% over 4 h. In contrast, depuration of the 20-nm beads was less extensive, reaching 40% over 4 h. Transmission electron microscopy confirmed uptake of 1,000-nm beads, but uptake of 20-nm beads was inconclusive since similar-sized inclusions could be observed in control treatments.

Diversity, biomass, and ecosystem processes in the marine benthos

Recent studies in terrestrial, plant-dominated systems have shown that reductions in diversity can affect essential ecosystem processes, especially productivity. However, the exact form of the relationship between diversity and ecosystem functions remains unknown, as does the relevance of these studies to other systems. We studied the relationships between macroinvertebrate species richness and ecosystem functions in a soft-bottom, intertidal system. We also considered, as a separate variable, the effects of macroinvertebrate biomass on ecosystem functions. A field experiment was conducted at Blackness, a mudflat in the Firth of Forth, Scotland, United Kingdom, using cages with different mesh sizes (195, 300, and 3000 μm) to establish low, medium, and high species richness treatments through differential colonization of defaunated sediments. Low, medium, and high biomass treatments were established by enclosing differing amounts of ambient sediment in defaunated plots. Other treatments controlled for the effects of defaunation and caging. The experiment ran for six weeks in the summer of 1999. All treatments contained species within the same five main functional groups of macroinvertebrate, but species identity varied both within and between treatments (thus species richness was considered a random, rather than fixed, variable). A total of 27 macroinvertebrate species were sampled across all treatments; 37% of these occurred in the low, 52% in the medium, and 74% in the high diversity treatments. n nAt the end of the experiment, the following physical variables were measured as indicators of ecosystem functions such as sediment stabilization and nutrient fluxes: sediment shear strength (a measure of sediment cohesiveness), water content, silt/clay content, organic content, redox potential (a measure of anoxia), nitrate, nitrite, phosphate and ammonium fluxes, and community respiration. Changes in biomass and species richness were found to have significant effects on oxygen consumption; these relationships were driven in particular by the presence of the largest species in our study, Nephtys hombergii. All other variables were not significantly affected by the treatments. These results support the null hypotheses of no relationship between ecosystem functions and diversity and biomass. However, our experiment was necessarily limited in both spatial and temporal scale; the implications of this when scaling up to larger scale generalizations are discussed. Our results suggest that diversity/biomass/ecosystem function relationships in the soft sediment benthos are likely to be very complex and may depend more on functional groups than species richness.

Assessing exposure, uptake and toxicity of silver and cerium dioxide nanoparticles from contaminated environments

The aim of this project was to compare cerium oxide and silver particles of different sizes for their potential for uptake by aquatic species, human exposure via ingestion of contaminated food sources and to assess their resultant toxicity. The results demonstrate the potential for uptake of nano and larger particles by fish via the gastrointestinal tract, and by human intestinal epithelial cells, therefore suggesting that ingestion is a viable route of uptake into different organism types. A consistency was also shown in the sensitivity of aquatic, fish cell and human cell models to Ag and CeO2 particles of different sizes; with the observed sensitivity sequence from highest to lowest as: nano-Ag > micro Ag > nano CeO2 = micro CeO2. Such consistency suggests that further studies might allow extrapolation of results between different models and species.

Effects of macroalgal mats on intertidal sandflats: an experimental study.

The growth of green macroalgal mats is becoming increasingly common in many marine intertidal habitats. While the ecological effects of such growth has previously been experimentally investigated on mudflats, such experiments have rarely been performed on intertidal sandflats. This study investigated the ecological effects of macroalgal cover on a moderately exposed intertidal sandflat, Drum Sands, Firth of Forth, Scotland. Artificially implanted Enteromorpha prolifera (Müller) caused marked changes in the macrobenthos, together with significant changes in all the measured sediment variables. After 6 weeks, the weed significantly increased the macrofaunal diversity. The numbers of Pygospio elegans (Claparède) were significantly reduced under weed mats, while those of Capitella capitata (Fabricius), oligochaetes and gammarids increased. Percent water, organics and silt/clay contents, medium phi and sorting coefficient significantly increased in the sediments under weed mats which also became significantly more reduced between 1 and 8 cm depth. After 20 weeks, a macrofaunal community numerically dominated by C. capitata, with a significantly reduced diversity, was present under weed mats, while sediment variables were no longer significantly different from controls. The negative effect of E. prolifera on P. elegans was mainly due to larval filtering, suggesting that weed is likely to have detrimental effects on population maintenance of most species which rely on planktonic larval recruitment. These results are broadly similar to those obtained from algal manipulation experiments performed in much more sheltered, muddier environments. We suggest that a predictable deterioration in environmental quality results from the growth of macroalgal mats in soft-bottom habitats. However, the longer term effects of such algal growth are less predictable and depend upon the spatial distributions of the most abundant infaunal species and the spatial heterogeneity of weed mat establishment.

Dense aggregations of Pygospio elegans (Claparède): effect on macrofaunal community structure and sediments

Abstract Epibenthic biogenic structures such as polychaete tubes are conspicuous features of many marine soft-bottom habitats. This paper compares the benthic macrofauna in patches with high and low densities of the tube-dweller Pygospio elegans on intertidal sandflats in eastern Scotland (UK). The main aim of this study was to determine potential differences in the macrofaunal community structure, the size distribution of individual species and sediment properties. Multivariate data analyses revealed that the macrofaunal community composition (excluding P. elegans ) within patches was always significantly different from outside patches, mainly due to variability in the abundances of Cerastoderma edule and Corophium volutator . In addition to P. elegans , 5 taxa were sufficiently abundant for univariate analyses, 4 of these ( Capitella capitata , C. edule , Macoma balthica and C. volutator ) being significantly more abundant within P. elegans patches than in surrounding, non-patch sediments. The size distribution of P. elegans was significantly different between patches (bimodal distribution) and non-patches (skewed distribution). Similarly, there was a greater proportion of larger C. capitata individuals within patches compared to non-patch sediments. Sediment organic content and silt/clay fraction were always significantly higher in patch sediments while redox profiles showed no differences except at the end of the study period when the top 2 cm within patches were more positive and more negative at 4 cm. These results imply that even relatively small (1–1.5 m 2 ) P. elegans patches can have large effects on the spatial variability of macrofaunal community structure on intertidal sandflats. Towards the end of the study there were marked visual changes in the P. elegans patches, such as wave-ripple marks on the surface, which signified their demise. This coincided with dramatic changes in the invertebrate community structure within patches. Along with the decline in P. elegans numbers, dramatic increases in the densities of the 2 bivalve species C. edule and M. balthica occurred, while remaining comparatively stable outside patches. This suggested that the conditions within P. elegans patches were particularly favourable to successful bivalve spat settlement. We postulate that P. elegans patches have limited longevity and propose that enhanced bivalve competition within them leads to rapid decreases in P. elegans numbers.